The increasing proportion of automation over the last 30 years in avionics, both civilian and military, has led to the increasing use by the crews of electronic systems, and less and less direct influence on the primary piloting controls of the aircraft.
This trend has been accentuated over the last twenty years with the generalization of onboard flight management systems, commonly referred to as FMS.
A flight management system consists of various functional components that enable the crew to program a flight from a navigation database. The system then calculates a lateral and vertical trajectory making it possible to reach the destination of the flight plan based on the characteristics of the aeroplane and the data supplied by the crew, and the environment of the system. The positioning and guidance functions collaborate to help the aircraft remain on this trajectory.
The interface functions with the crew and with the ground are used to place man in the navigation loop, because only he can be responsible for the progress of the flight.
When the operator needs to perform an emergency manoeuvre, such as in the event of a depressurization, he must follow a documented procedure that begins in accordance with the regulations with separation from the route that is assigned to him with an angle, generally of 45°, then descent to the altitude of 10 000 feet so that people, notably the crew, the commercial personnel and the passengers onboard the aircraft can breathe normally.
It often happens that the aircraft can continue to its destination at this altitude while following a route parallel to the one that was assigned to it.
This manoeuvre is complicated when the aircraft is flying over mountainous regions, preventing it from descending directly to the altitude of 10 000 feet.
An airline company flying over these types of area must therefore prepare particular procedures, called “escape routes”, making it possible to reach the correct altitude, while avoiding the relief, and before the oxygen generator has exhausted its resources.
The company Northwest Airlines has, for example, developed a procedure of this type for its fleet of Airbus A330 flying over Greenland, Iran and Afghanistan.
A number of functions to assist in the management of a pressurization failure are known, mainly based on a knowledge of the surrounding terrain or on taking automatic control of the aircraft by a system. In case of depressurization, the crew may have difficulties in analyzing the information displayed on the screens in manual piloting mode, considering the short space of time in which it must act.
Given the context of sequencing manoeuvres while continuing to navigate, the use of a flight management system, such as the FMS, is appropriate to lighten the workload of the crew and its stress in this oppressive situation.
Currently, the operator has a number of tools, such as, for example, the OFFSET function. The latter makes it possible to deviate from the assigned route by programming a modifiable capture angle, then following a parallel route. The FMS is capable of managing a trajectory parallel to the flight plane with modifiable capture angle. In emergency cases, a modifiable capture angle may be 45° for example.
One problem is that the FMS does not these days manage a flight plan portion comprising a descent profile taking into account relief variations or obstacles and does not adapt the descent according to the outside environment.
The FMS can manage scheduled changes of altitude, but based on geographic positions or on optimization criteria. The operator can then calculate the position at which the aeroplane is located at a given instant and insert a change of level from that point.
However, this operation is unrealistic in a stress situation, for example in the event of a depressurization. Weather events may mean that the point initially calculated is reached later than planned, which means that the crew has to completely manage this procedure according to the time that has passed since the problem of depressurization of the aircraft was detected.
To manage the depressurization of an aircraft, the operator currently has only a written procedure and his knowledge of the aeroplane system.
The invention makes it possible to overcome the abovementioned drawbacks.